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Use of Label Switching on Frame Relay Networks Specification
RFC 3034

Document type: RFC - Proposed Standard (January 2001; No errata)
Document stream: IETF
Last updated: 2013-03-02
Other versions: plain text, pdf, html

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IESG State: RFC 3034 (Proposed Standard)
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Network Working Group                                           A. Conta
Request for Comments: 3034                        Transwitch Corporation
Category: Standards Track                                      P. Doolan
                                                                Ennovate
                                                                A. Malis
                                                   Vivace Networks, Inc.
                                                            January 2001

             Use of Label Switching on Frame Relay Networks
                             Specification

Status of this Memo

   This document specifies an Internet standards track protocol for the
   Internet community, and requests discussion and suggestions for
   improvements.  Please refer to the current edition of the "Internet
   Official Protocol Standards" (STD 1) for the standardization state
   and status of this protocol.  Distribution of this memo is unlimited.

Copyright Notice

   Copyright (C) The Internet Society (2001).  All Rights Reserved.

Abstract

   This document defines the model and generic mechanisms for
   Multiprotocol Label Switching on Frame Relay networks.  Furthermore,
   it extends and clarifies portions of the Multiprotocol Label
   Switching Architecture described in [ARCH] and the Label Distribution
   Protocol (LDP) described in [LDP] relative to Frame Relay Networks.
   MPLS enables the use of Frame Relay Switches as Label Switching
   Routers (LSRs).

Table of Contents

   1. Introduction................................................2
   2. Terminology.................................................3
   3. Special Characteristics of Frame Relay Switches.............4
   4. Label Encapsulation.........................................5
   5. Frame Relay Label Switching Processing......................6
   5.1  Use of DLCIs..............................................6
   5.2  Homogeneous LSPs..........................................7
   5.3  Heterogeneous LSPs........................................7
   5.4  Frame Relay Label Switching Loop Prevention and Control...7
   5.4.1   FR-LSRs Loop Control - MPLS TTL Processing.............7
   5.4.2   Performing MPLS TTL calculations.......................8
   5.5  Label Processing by Ingress FR-LSRs......................12

Conta, et al.               Standards Track                     [Page 1]
RFC 3034            Label Switching with Frame Relay        January 2001

   5.6  Label Processing by Core FR-LSRs.........................12
   5.7  Label Processing by Egress FR-LSRs.......................13
   6.  Label Switching Control Component for Frame Relay.........13
   6.1  Hybrid Switches (Ships in the Night)  ...................14
   7.  Label Allocation and Maintenance Procedures ..............15
   7.1  Edge LSR Behavior........................................15
   7.2  Efficient use of label space-Merging FR-LSRs.............18
   7.3  LDP message fields specific to Frame Relay...............19
   8.  Security Considerations  .................................21
   9.  Acknowledgments  .........................................21
   10. References  ..............................................22
   11. Authors' Addresses  ......................................23
   12. Full Copyright Statement  ................................24

1. Introduction

   The Multiprotocol Label Switching Architecture is described in
   [ARCH].  It is possible to use Frame Relay switches as Label
   Switching Routers.  Such Frame Relay switches run network layer
   routing algorithms (such as OSPF, IS-IS, etc.), and their forwarding
   is based on the results of these routing algorithms.  No specific
   Frame Relay routing is needed.

   When a Frame Relay switch is used for label switching, the top
   (current) label, on which forwarding decisions are based, is carried
   in the DLCI field of the Frame Relay data link layer header of a
   frame.  Additional information carried along with the top (current)
   label, but not processed by Frame Relay switching, along with other
   labels, if the packet is multiply labeled, are carried in the generic
   MPLS encapsulation defined in [STACK].

   Frame Relay permanent virtual circuits (PVCs) could be configured to
   carry label switching based traffic.  The DLCIs would be used as MPLS
   Labels and the Frame Relay switches would become Frame Relay Label
   Switching Routers, while the MPLS traffic would be encapsulated
   according to this specification, and would be forwarded based on
   network layer routing information.

   The keywords MUST, MUST NOT, MAY, OPTIONAL, REQUIRED, RECOMMENDED,
   SHALL, SHALL NOT, SHOULD, SHOULD NOT are to be interpreted as defined
   in RFC 2119.

   This document is a companion document to [STACK] and [ATM].

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